Petroleum oil is today's most valuable commodity. It is the best source of fuel, tar, waxes, metallurgical coke and chemical precursors for most of the organic chemical industry. Crudely put, petroleum oil is product of fossilized organisms subjected to the tremendous pressure under layers of Earth's crust. Naturally, it takes a few million years for fossils to convert to a petroleum reservoir. Many of such reservoirs are formed under the sea. Those which are not are believed to be once part of the sea. Thus, most reservoirs have a bed of mineral salt nearby. Organisms that are now fossilized have their organic matter converted into petroleum and minerals are incorporated into salt deposits. Common method for harvesting these oil fields is to drill to the reservoir and utilize the pressure by the petroleum gases that are built up and extract the oil underneath. If such pressure is insufficient, artificial driving force is provided with pressurized water. This results into better rate of production of the oil.
Oil produced from the well contains water in an emulsion form. Most of the time, oil is in continuous phase and water in the dispersed phase. This emulsion cannot be sent to refineries without separation. Reason being it increases processing cost of oil since water has large latent heat of vaporization. Hence, only solutions to this issue are mechanical and chemical demulsifiers; emulsion breakers that mechanically or through addition of a chemical will allow the phases to separate.
Platforms that operate on offshore oilfields usually cannot afford mechanical demulsifiers. They occupy too much space and hence, chemical demulsifiers are best suited for them. Choice of chemical demulsifier is important. Many factors, most importantly composition of the oil, affects this choice. Resin and asphaltene which are insoluble in heptanes and are usually suspended as colloids enhance stability of the emulsion. Oils with more asphaltene content form more stable emulsions and oils with more resinous content form weaker emulsions.
Chemical demulsification is an economic, convenient and efficient method for breaking water in oil emulsions. The function of the demulsifier is to modify the interfacial properties and displace the asphaltenic stabilized emulsion film from the oil/water interface.
Amphiphilic block copolymers, which contain hydrophilic ethylene oxide (EO) and hydrophobic propylene oxides (PO) blocks, are commercially available and widely used as demulsifiers. The structure of a demulsifier can influence the interfacial properties and cause displacement of the emulsion film. The performance of the demulsifier strongly depends on its chemical characteristics, chemical composition, MW, oil/water interfacial tension etc. However, ethylene oxide (EO) or propylene oxides (PO) are toxic, explosive and deadly carcinogens. Since PFRs require alkoxylation through EO and PO, they are difficult to work on as well.
U.S. Pat. No. 7,470,744 B2 discloses a copolymer useful as a demulsifier or water clarifier may be prepared by polymerizing at least one aromatic monomer having one or more polymerizable double bonds; at least one oleophilic monomer having one or more polymerizable double bonds; at least one ionizable monomer having a polymerizable double bond; and at least one hydrophilic monomer having one or more polymerizable double bonds, under polymerization conditions sufficient to prepare a copolymer.
Therefore, there is need to develop cost effective demulsifier which can work at lower temperature and lower dosages for separation of water from crude oil.